Process for making inactive menthol



[UNITED STATES Patented Sept. 23, 1930 time ' KARL scHoLLxoPr, ornussnnnonn-onnnxassnng l ng-names. serum, or DUSSEL- DORF-HEERDT,GERMANY, assrenons To.nnnmisonnKAMPFERJABRIK cnsnLL, SGHAF'I MITIBESCHRANKTER HAFTUNG, or DUSSELDORF-OBERKASSEL, GERMANY PROCESS FORMAKING INAC'IIVE MENTI- IOL No Drawing. Original application filed. June30, 1927, Serial No. 202,739, andin Germany February 15, 1927. Dividedand this application filed September 20, 1928. Serial No. 307,332.

This is a process for the production of inactive menthol, new isomer ofinactive menthol and making the same, being a divisional application ofapplication Serial No. 202,739 filed J 11116 30th, 1927.

According to this process inactive neomenthol is transformed to inactivementhol. This transformation maybe effected by the action of mentholatesof the alkali forming metals at temperatures above 100 degreescentigrade, the inactive neomenthol being employed by itself or inadmixture with other isomers of inactive menthol and sepa rating thecrude inactive menthol from the resulting mixture by physical methodsfor instance by freezing-out or fractional distillation, purifying thecrude inactive menthol by way of its esters as described in U. S. PatentNo. 1,672,346, and transforming the residual isomers anew. I r

Example 1.-300 kilograms inactive neomenthol and 9 kilograms of metallicsodium are dissolved in the warm and the mixture with the resultingsodium mentholates is heated at 180 degrees centigrade for about 24hours. The resulting menthols mixture is thereupon distilled oif withsteam or also shaken with water until the alkali reaction is no longerin evidence and the crude inactive menthol is separated from theequilibrium mixture obtained by freezing or fractional distillation orboth and is further purified by way of the crystallized esters.Completely pure inactive menthol of melting point 3436 degreescentigrade is obtained. The isomeric menthols resulting from theseparation and purification of the inactive menthol are transformedafresh.

Ewample 2.In a mixture of:

100 kilograms of inactive neomenthol, melting point 51 degreescentigrade,

l00 kilograms of inactive neo-isomenthol, melting point 12-14 degreescentigrade,

100 kilograms of inactive isomenthol, melting point 53 degreescentigrade,

9 kilograms of metallic sodium are dis solved in the warm and themixture with the resulting sodium mentholates is heated at 180 degreescentigrade for about 24 hours.

The resulting menthols mixture is thereupon distilled off with steam oralso shaken with water until the alkali reaction is no longer inevidence andthe crude inactive menthol is separated from the equilibriummixture obtained by freezing or fractional distillation or both and isfurther purified by way of'the crystallized esters. Completely pure'inmenthol, theracemate of natural menthol,

which consists in heating inactive neomenthol with mentholates of thealkali forming metals and separating from the reaction product crudeinactive menthol by physical methods.

2. The process for manufacturing inactive menthol, the racemate ofnatural menthol,

which consists in heating inactive neomenthol admlxed with other isomersof inactive menthol, with mentholates of the alkali forming metals andseparating from the reaction product crude inactive menthol by physicalmethods.

3. The process for manufacturing inactive menthol, the racemate ofnatural menthol,

which consists in heating inactive neomen thol with mentholates of thealkali forming metals and separating from the reaction product crudeinactive menthol by fractional distillation.

4. The process of manufacturing inactive menthol, the racemate ofnatural menthol,

which consists in heating inactive neomenthol with mentholates of thealkali forming metals, separating crude inactive menthol from thereaction product, and purifying said crude inactive menthol.

5. The process for manufacturing inactive menthol, the racemate ofnatural menthol, which consists in heating inactive neomenthol withmentholates of the alkali forming metals and separating from thereaction product crude inactive menthol by fractional crystallization.

In testimony whereof We aflix our 'signatures.

'KARL soHoLLKoPF.

ARTHUR SERINL:

r so 7

